Abstract:

The present invention relates to catalysts component for the
polymerization of ethylene and its mixtures with olefins
CH2═CHR, wherein R is an alkyl, cycloalkyl or aryl radical
having 1-12 carbon atoms, comprising Ti, Mg, halogen, and electron donor
belonging to 1,2-diethers as internal electron donor compound. The
catalyst of the invention is suitably used in (co)polymerization
processes of ethylene to prepare (co)polymers having narrow Molecular
Weight Distribution (MWD) and high bulk density.

Claims:

1-9. (canceled)

10. Substantially spherical catalyst components for polymerizing of
olefins comprising Mg, Ti, halogen, and an electron donor compound of
formula (I):RaCR1(OR4)--CR2R3(OR5)
(I)whereinRa is methyl or hydrogen, or is condensed with R4 to
form a cycle;R1, R2 and R3 are, independently, hydrogen or
C1-C20 hydrocarbon groups optionally comprising
heteroatoms;R4 and R5 are, independently, C1-C20
alkyl groups or R6CO-- groups, or R4 and R5 can be joined
with R and R3 respectively to form a cycle; andR6 is a
C1-C20 alkyl group;with the provisos that when Ra is
hydrogen R4 and R5 are not simultaneously methyl, and when
Ra and R4 form a cycle R5 is a C1-C20 alkyl
group.

15. The catalyst components according to claim 10, wherein the Ti are from
a titanium compound comprising at least one Ti-halogen bond, and the Mg
are from magnesium chloride.

16. The catalyst components according to claim 10, wherein the catalyst
components are obtained by reacting a titanium compound comprising at
least one Ti-halogen bond, with substantially spherical particles of an
adduct of formula MgCl.sub.2.nROH, in presence of the electron donor
compound of formula (I), wherein n is from 1 to 6, and R is an alkyl,
cycloalkyl or aryl radical comprising 1-12 carbon atoms.

17. A catalyst for polymerizing olefins of formula CH.sub.2.dbd.CHR',
wherein R' is hydrogen or a hydrocarbyl radical comprising 1-12 carbon
atoms, the catalyst comprising a product of a reaction between:(a) a
catalyst component comprising Mg, Ti, halogen, and an electron donor
compound of formula
(I):RaCR1(OR4)--CR2R3(OR5)
(I)whereinRa is methyl or hydrogen, or is condensed with R4 to
form a cycle;R1, R2 and R3 are, independently, hydrogen or
C1-C20 hydrocarbon groups optionally comprising
heteroatoms;R4 and R5 are, independently, C1-C20
alkyl groups or R6CO-- groups, or R4 and R5 can be joined
with R and R3 respectively to form a cycle; andR6 is a
C1-C20 alkyl group;with the provisos that when Ra is
hydrogen R4 and R5 are not simultaneously methyl, and when
Ra and R4 form a cycle R5 is a C1-C20 alkyl
group; and(b) an alkylaluminum compound.

18. A process for polymerizing olefins of formula CH.sub.2.dbd.CHR',
wherein R' is hydrogen or a hydrocarbyl radical comprising 1-12 carbon
atoms, the process being carried out in presence of a catalyst, the
catalyst comprising a product of a reaction between:(a) a catalyst
component comprising Mg, Ti, halogen, and an electron donor compound of
formula (I):RaCR1(OR4)--CR2R3(OR5)
(I)whereinRa is methyl or hydrogen, or is condensed with R4 to
form a cycle;R1, R2 and R3 are, independently, hydrogen or
C1-C20 hydrocarbon groups optionally comprising
heteroatoms;R4 and R5 are, independently, C1-C20
alkyl groups or R6CO-- groups, or R4 and R5 can be joined
with R and R3 respectively to form a cycle; andR6 is a
C1-C20 alkyl group;with the provisos that when Ra is
hydrogen R4 and R5 are not simultaneously methyl, and when
Ra and R4 form a cycle R5 is a C1-C20 alkyl
group; and(b) an alkylaluminum compound.

Description:

[0001]The present invention relates to catalyst components for the
polymerization of ethylene and its mixtures with olefins
CH2═CHR, wherein R is an alkyl, cycloalkyl or aryl radical
having 1-12 carbon atoms, comprising Ti, Mg, halogen, and a particular
electron donor compound. The catalyst component of the invention is
suitably used in (co)polymerization processes of ethylene to prepare
(co)polymers having narrow Molecular Weight Distribution (MWD), high bulk
density and wide range of average particle size. The MWD is an important
characteristic of ethylene polymers in that it affects their rheological
behavior, their processability, and their final mechanical properties. In
particular, polymers with narrow MWD are suitable for films and injection
molding in that deformation and shrinkage problems in the manufactured
article are minimized. The width of the molecular weight distribution for
the ethylene polymers is generally expressed as melt flow ratio F/E,
which is the ratio between the melt index measured by a load of 21.6 Kg
(melt index F) and that measured with a load of 2.16 Kg (melt index E).
The measurements of melt index are carried out according to ASTM D-1238
and at 190° C. Catalysts for preparing ethylene (co)polymers
having narrow MWD are described in the European patent application
EP-A-373999. The catalyst comprises a solid catalyst component consisting
of a titanium compound supported on magnesium chloride, an alkyl-Al
compound and an electron donor compound (external donor) selected from
monoethers of the formula R'OR''. Good results in terms of narrow MWD are
only obtained when the solid component also contains an internal electron
donor compound (diisobutylphthalate). The catalyst activity is rather low
and, in addition, the cited document does not disclose or teach anything
about the polymer bulk density provided by the catalyst. This latter
characteristic is very important in the operation of the plants because
it assures smooth polymer flow and high productivity. Hence, it would be
highly desirable to have a catalyst capable to produce polymers in high
yields with narrow molecular weight distribution and high bulk density.

[0002]Moreover, it would be also desirable that the catalyst component be
able to produce polymers having a variable and flexible range of average
particle size in order to broaden the range of applicability and making
possible their use also in gas-phase polymerization technology.

[0003]JP 2003-321511 discloses polymerization of ethylene in the presence
of a catalyst the preparation of which includes the use of Mg metal,
oxygenated compounds, among which 1,2-dimethoxypropane, a titanium
compound to form a gel-like solution from which a solid is precipitated
by the aid of a chlorinating agent. Although polymers with narrow MWD and
high bulk density are obtained, the average particle size of the polymer
is not large enough to allow the use in gas-phase polymerization.

[0004]The applicant has now found catalyst components in substantially
spherical form capable of satisfying the above-mentioned needs that
comprise Mg, Ti, and halogen as essential elements and containing an
electron donor compound of formula (I)

RaCR1(OR4)--CR2R3(OR5) (I)

in which Ra is a methyl group or hydrogen or is condensed with
R4 to form a cycle, R1, R2 and R3 are, independently,
hydrogen or C1-C20 hydrocarbon groups, possibly containing heteroatoms,
R4 and R5 are C1-C20 alkyl groups, or R6CO-- groups where
R6 is a C1-C20 alkyl group, or they can be joined with R and R3
respectively to form a cycle; with the provisos that when Ra is
hydrogen R4 and R5 are not simultaneously methyl and when
Ra and R4 form a cycle R5 is C1-C20 alkyl group.

[0005]Preferably, in the electron donor compound of formula (I), Ra
is methyl.

[0006]Preferably, in the electron donor compound of formula (I) R1 to
R3 are hydrogen. When R4 and R5 are alkyl groups they are
preferably chosen among C1-C5 alkyl groups and more preferably among
methyl or ethyl. Preferably they are both methyl. Among R6CO groups
preferred is acetyl.

[0008]The term substantially in spherical form means particles in which
the ratio among the longer axis and the shorter axis is equal to, or
lower than, 1.5 and preferably lower than 1.3. Such values can be measure
via known methods such as optical or electronic microscopy.

[0009]Particularly preferred are the solid catalyst components in which
the Ti atoms derive from a titanium compound which contains at least one
Ti-halogen bond and the Mg atoms derive from magnesium chloride. In a
still more preferred aspect both the titanium compound and the electron
donor of formula (I) are supported on magnesium dichloride. Preferably,
in the catalyst of the present invention at least 70% of the titanium
atoms and more preferably at least 90% of them, are in the +4 valence
state.

[0010]In a particular embodiment, the magnesium dichloride is in active
form. The active form of magnesium dichloride present in the catalyst
components of the invention is recognizable by the fact that in the X-ray
spectrum of the catalyst component the major intensity reflection which
appears in the spectrum of the non-activated magnesium dichloride (having
usually surface area smaller than 3 m2/g) is no longer present, but
in its place there is a halo with the position of the maximum intensity
shifted with respect to the position of the major intensity reflection,
or by the fact that the major intensity reflection presents a half-peak
breadth at least 30% greater that the one of the corresponding reflection
of the non-activated Mg dichloride. The most active forms are those in
which the halo appears in the X-ray spectrum of the solid catalyst
component.

[0011]In the case of the most active forms of magnesium dichloride, the
halo appears in place of the reflection which in the spectrum of the
non-activated magnesium chloride is situated at the interplanar distance
of 2.56 Å.

[0012]Preferred titanium compounds are the halides or the compounds of
formula TiXn(OR7)4-n, where 1≦n≦3, X is
halogen, preferably chlorine, and R7 is C1-C10 hydrocarbon
group. Especially preferred titanium compounds are titanium tetrachloride
and the compounds of formula TiCl3OR7 where R7 has the
meaning given above and in particular selected from methyl, n-butyl or
isopropyl.

[0013]One preferred way to prepare the substantially spherical catalyst
components is by reacting the titanium compound having at least a
Ti-halogen bond with an adduct of formula a MgCl2.nROH adduct in the
form of substantially spherical particles, where n is generally from 1 to
6, and ROH is an alcohol in the presence of the electron donor of formula
(I).

[0014]In particular, the MgCl2.nROH is caused to react with an excess
of liquid TiCl4 containing electron donor of formula (I) in the
optional presence of hydrocarbon solvents. The reaction temperature
initially is from 0° to 25° C., and is then increased to
80-135° C. Then, the solid may be reacted once more with
TiCl4, separated and washed with a liquid hydrocarbon until no
chlorine ions can be detected in the wash liquid. The electron donor
compound of formula (I) is preferably added together with the titanium
compound to the reaction system. However, it can also be first contacted
with the adduct alone and then the so formed product reacted with the
titanium compound. As an alternative method, the electron donor compound
can be added after the completion of the reaction between the adduct and
the titanium compound.

[0015]The MgCl2.nROH adduct can be prepared in spherical form from
melted adducts, by emulsifying the adducts in a liquid hydrocarbon and
thereafter causing them to solidify by fast quenching. Representative
methods for the preparation of these spherical adducts are reported for
example in U.S. Pat. No. 4,469,648, U.S. Pat. No. 4,399,054, and
WO98/44009. Another useable method for the spherulization is the spray
cooling described for example in U.S. Pat. Nos. 5,100,849 and 4,829,034.

[0016]In a preferred aspect of the present invention, before being reacted
with the titanium compound, the spherulized adducts are subjected to
thermal dealcoholation at a temperature ranging from 50 and 150°
C. until the alcohol content is reduced to values lower than 2 and
preferably ranging from 0.3 and1.5 mols per mol of magnesium chloride.

[0017]Optionally, said dealcoholated adducts can be finally treated with
chemical reagents capable of reacting with the OH groups of the alcohol
and of further dealcoholating the adduct until the content is reduced to
values which are generally lower than 0.5 mols.

[0018]The MgCl2/electron donor of formula (I) molar ratio used in the
reactions indicated above preferably ranges from 7:1 to 40:1, preferably
from 8:1 to 35:1.

[0019]The particle size of the catalyst components obtained with this
method is easily controllable and can vary over a broad range for example
from 1 to 150 μm. This allows the preparation of both components with
a small average particle size (in the range of 5-20 μm) useful for
slurry polymerization and components with a medium large particle size
(over 30 μm) particularly suitable for gas-phase polymerization. Also
the particle size distribution is narrow being the SPAN of the catalyst
particles comprised between 0.7 and 1.3 preferably from 0.8 to 1.2. The
SPAN being defined as the value of the ratio

P 90 - P 10 P 50 , ##EQU00001##

wherein P90 is the value of the diameter such that 90% of the total volume
of particles have a diameter lower than that value; P10 is the value of
the diameter such that 10% of the total volume of particles have a
diameter lower than that value and P50 is the value of the diameter such
that 50% of the total volume of particles have a diameter lower than that
value. In particular, with the catalyst of the invention it is possible
to produce polymers with average particle size over 350 μm,
particularly over 500 μm which would be suitable for gas-phase
polymerization and are not obtained in JP 2003-321511. Moreover, the said
polymers are also endowed with a narrow molecular weight distribution
(F/E ratio lower than 30) and a high bulk density (typically over 0.3
g/cm3).

[0020]The solid catalyst components according to the present invention are
converted into catalysts for the polymerization of olefins by reacting
them with organoaluminum compounds according to known methods.

[0021]In particular, it is an object of the present invention a catalyst
for the polymerization of olefins CH2═CHR, in which R is
hydrogen or a hydrocarbyl radical with 1-12 carbon atoms, comprising the
product of the reaction between:

[0022](a) a solid catalyst component as described above,

[0023](b) an alkylaluminum compound and, optionally,

[0024](c) an external electron donor compound.

[0025]The alkyl-Al compound can be preferably selected from the trialkyl
aluminum compounds such as for example trimethylaluminum (TMA),
triethylaluminum (TEAL), triisobutylaluminum (TIBA)),
tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum. Also
alkylaluminum halides and in particular alkylaluminum chlorides such as
diethylaluminum chloride (DEAC), diisobutylalumunum chloride,
Al-sesquichloride and dimethylaluminum chloride (DMAC) can be used. It is
also possible to use, and in certain cases preferred, mixtures of
trialkylaluminum's with alkylaluminum halides. Among them mixtures
between TEAL and DEAC are particularly preferred. The use of TEAL and
TIBA, alone or in mixture is also preferred. Particularly preferred is
also the use of TMA.

[0026]The external electron donor compound can be selected from the group
consisting of ethers, esters, amines, ketones, nitriles, silanes and
mixtures of the above. In particular, it can advantageously be selected
from the C2-C20 aliphatic ethers and in particulars cyclic ethers
preferably having 3-5 carbon atoms cyclic ethers such as
tetrahydrofurane, dioxane.

[0027]In addition, the electron donor compound can also be advantageously
selected from silicon compounds of formula
Ra5Rb6Si(OR7)c, where a and b are integer
from 0 to 2, c is an integer from 1 to 3 and the sum (a+b+c) is 4;
R5, R6, and R7, are alkyl, cycloalkyl or aryl radicals
with 1-18 carbon atoms optionally containing heteroatoms. Particularly
preferred are the silicon compounds in which a is 0, c is 3, R6 is a
branched alkyl or cycloalkyl group, optionally containing heteroatoms,
and R7 is methyl. Examples of such preferred silicon compounds are
cyclohexyltrimethoxysilane, t-butyltrimethoxysilane and
thexyltrimethoxysilane.

[0028]The above mentioned components (a)-(c) can be fed separately into
the reactor where, under the polymerization conditions can exploit their
activity. It may be advantageous the pre-contact of the above components,
optionally in the presence of small amounts of olefins, for a period of
time ranging from 0.1 to 120 minutes preferably in the range from 1 to 60
minutes. The pre-contact can be carried out in a liquid diluent at a
temperature ranging from 0 to 90° C. preferably in the range of 20
to 70° C.

[0029]The catalyst system disclosed above can be used directly in the main
polymerization process or alternatively, it can be pre-polymerized
beforehand. A pre-polymerization step is usually preferred when the main
polymerization process is carried out in the gas phase. The
prepolymerization can be carried out with any of the olefins
CH2═CHR, where R is H or a C1-C10 hydrocarbon group. In
particular, it is especially preferred to pre-polymerize ethylene,
propylene or mixtures thereof with one or more α-olefins, said
mixtures containing up to 20% in moles of α-olefin, forming amounts
of polymer from about 0.1 g per gram of solid component up to about 1000
g per gram of solid catalyst component. The pre-polymerization step can
be carried out at temperatures from 0 to 80° C., preferably from 5
to 70° C., in the liquid or gas phase. The pre-polymerization step
can be performed in-line as a part of a continuous polymerization process
or separately in a batch process. The batch pre-polymerization of the
catalyst of the invention with ethylene in order to produce an amount of
polymer ranging from 0.5 to 20 g per gram of catalyst component is
particularly preferred. The pre-polymerized catalyst component can also
be subject to a further treatment with a titanium compound before being
used in the main polymerization step. In this case the use of TiCl4
is particularly preferred. The reaction with the Ti compound can be
carried out by suspending the prepolymerized catalyst component in the
liquid Ti compound optionally in mixture with a liquid diluent; the
mixture is heated to 60-120° C. and kept at this temperature for
0.5-2 hours.

[0030]The catalysts of the invention can be used in any kind of
polymerization process both in liquid and gas-phase processes. Catalysts
in which the solid catalyst component has small average particle size,
such as less than 30 μm, preferably ranging from 5 to 20 μm, are
particularly suited for slurry polymerization in an inert medium, which
can be carried out continuously stirred tank reactor or in loop reactors.
In a preferred embodiment the solid catalyst components having small
average particle size as described are particularly suited for the use in
two or more cascade loop or stirred tank reactors producing polymers with
different molecular weight and/or different composition in each reactor.
Catalysts in which the solid catalyst component has medium/large average
particle size such as at least 30 μm and preferably ranging from 50 to
100 μm are particularly suited for gas-phase polymerization processes
which can be carried out in agitated or fluidized bed gas-phase reactors.
Also in this case use of the catalyst in plant set-up comprising two or
more cascade reactors working under different conditions to prepare
polymers with different molecular weight and/or composition is
particularly preferred.

[0031]As already mentioned, the catalysts of the present invention are
particularly suitable for preparing ethylene polymers having narrow
molecular weight distribution that are characterized by a F/E ratio of
lower than 30 in combination with a high bulk density. When ethylene is
polymerized together with a minor amount of an alpha-olefin as comonomer,
selected from propylene, buetene-1, hexene-1 and octene-1, a linear low
density polyethylene having a density lower than 0.940 g/cm3 is
obtained with a very good quality which is indicated by the low ratio
(lower than 1.4) among weight of xilene soluble fraction and weight
percentage of comonomer in the chain. In addition, the catalysts of the
invention also show the capability of producing polymers with a high bulk
density, typically over 0.3 g/cm3 and high activity, generally
higher than 30 Kg/g cat.

[0032]In addition, to the ethylene homo and copolymers mentioned above the
catalysts of the present invention are also suitable for preparing
very-low-density and ultra-low-density polyethylenes (VLDPE and ULDPE,
having a density lower than 0.920 g/cm3, to 0.880 g/cm3)
consisting of copolymers of ethylene with one or more alpha-olefins
having from 3 to 12 carbon atoms, having a mole content of units derived
from ethylene of higher than 80%; elastomeric copolymers of ethylene and
propylene and elastomeric terpolymers of ethylene and propylene with
smaller proportions of a diene having a content by weight of units
derived from ethylene of between about 30 and 70%.

[0033]The following examples are given in order to further describe the
present invention in a non-limiting manner.

CHARACTERIZATION

[0034]The properties are determined according to the following methods:

[0040]Fraction soluble in xylene. The solubility in xylene at 25°
C. was determined according to the following method: About 2.5 g of
polymer and 250 mL of o-xylene were placed in a round-bottomed flask
provided with cooler and a reflux condenser and kept under nitrogen. The
mixture obtained was heated to 135° C. and was kept under stirring
for about 60 minutes. The final solution was allowed to cool to
25° C. under continuous stirring, and was then filtered. The
filtrate was then evaporated in a nitrogen flow at 140° C. to
reach a constant weight. The content of said xylene-soluble fraction is
expressed as a percentage of the original 2.5 grams.

[0046]Into a 4.5 liters stainless steel autoclave, degassed under N2
stream at 70° C., 1.6 liters of anhydrous hexane, the reported
amount of catalyst component and 0.5 g of triethylaluminum (TEAL) were
introduced (or 0.87 g of TIBA). The whole was stirred, heated to
75° C. and thereafter 4 bar of H2 and 7 bar of ethylene were
fed. The polymerization lasted 2 hours during which ethylene was fed to
keep the pressure constant. At the end, the reactor was depressurized and
the polymer recovered was dried under vacuum at 60° C.

[0047]General Procedure for the LLDPE Polymerization Test

[0048]A 4.0 L stainless-steel autoclave equipped with a helical magnetic
stirrer, temperature and pressure indicator, feed line for ethylene,
propane, hydrogen, 1-butene and a steel vial for the injection of the
catalyst was used and purified by flushing ethylene at 80° C. and
washing with propane. In the following order, 1.2 g of TIBA (or 0.69 g of
TEAL) and 12 mg of the solid catalyst matured for 5 minutes and
introduced in the empty reactor in a stream of propane. The autoclave was
then closed and 1.6 l of propane were introduced, after which the
temperature was raised to 75° C. (10 minutes) with simultaneous
introduction of ethylene up to 7 bar of partial pressure and 1-butene in
the amount reported in table. At the end, 1.5 bar of hydrogen (partial
pressure) were added. Under continuous stirring, the total pressure was
maintained at 75° C. for 120 minutes by feeding ethylene (if the
ethylene consumption reaches 200 g, the test is stopped before the two
hours). At the end the reactor was depressurised and the temperature was
dropped to 30° C. The recovered polymer was dried at 60° C.
under a nitrogen flow and weighted.

EXAMPLE 1

[0049]Preparation of the Spherical MgCl2-EtOH Adduct

[0050]A magnesium chloride and alcohol adduct containing about 3 mols of
alcohol having spherical form and average size of about 12 μm was
prepared following the method described in example 2 of U.S. Pat. No.
4,399,054.

[0051]Preparation of the Solid Component

[0052]The spherical support, prepared according to the general method
underwent a thermal treatment, under N2 stream, over a temperature
range of 50-150° C. until spherical particles having a residual
ethanol content of about 35% (1.1 mole of ethanol for each MgCl2
mole) were obtained.

[0053]Into a 2 l glass reactor provided with stirrer, were introduced 1 L
of TiCl4, 70 g of the support prepared as described above and, at
temperature of 0° C., 3.6 ml of 1,2-diemthoxypropane (1,2DMP)
(Mg/DMP=16 mol/mol). The whole mixture was heated and kept under stirring
for 60 minutes at 100° C. After that, stirring was discontinued
and the liquid siphoned off. Two washings with fresh hexane (1 liter)
were performed at 60° C. and then, other two more hexane washings
were performed at room temperature. The spherical solid component was
discharged and dried under vacuum at about 50° C.

[0055]The so prepared catalyst has then been used in the polymerization of
ethylene according to the general polymerization procedure (first run
with TEAL second run with TIBAL). The results are shown in Table 1.

[0056]Moreover, the catalyst was also used in the preparation of LLDPE
according to the general procedure and the results shown in Table 2 have
been obtained.

EXAMPLE 2

[0057]The catalyst was prepared according to the procedure disclosed in
Example 1 with the difference that methyl tetrahydrofurfuryl ether was
used instead of 1,2DMP. The composition of the solid was the following:

[0058]The so prepared catalyst has then been used in the polymerization of
ethylene according to the general polymerization procedure (first run
with TEAL second run with TIBAL). The results are shown in Table 1.

EXAMPLE 3

[0059]The catalyst was prepared according to the procedure disclosed in
Example 1 with the difference that 1,2-diethoxypropane (1,2-DEP) in an
amount such the Mg/1,2-DEP is 8 is used. The composition of the solid was
the following:

[0060]The so prepared catalyst has then been used in the polymerization of
ethylene according to the general polymerization procedure (with TIBAL).
The results are shown in Table 1. Moreover, the catalyst was also used in
the preparation of LLDPE according to the general procedure and the
results shown in Table 2 have been obtained.

EXAMPLE 4

[0061]The catalyst was prepared according to the procedure disclosed in
Example 1 with the difference that treatment in TiCl4 was carried
out for 120 minutes and the solid phase settled in 120 minutes while
keeping constant the temperature of liquid phase.

[0062]The so prepared catalyst has then been used in the polymerization of
ethylene according to the general polymerization procedure (first run
with TEAL second run with TIBAL). The results are shown in Table 1.

EXAMPLE 5

[0063]The catalyst was prepared according to the procedure disclosed in
Example 1 with the difference that the settling time of the solid phase
was 180 minutes with temperature of the liquid phase being at 50°
C.

[0064]The so prepared catalyst has then been used in the polymerization of
ethylene according to the general polymerization procedure (first run
with TEAL second run with TIBAL). The results are shown in Table 1.

EXAMPLE 6

[0065]The catalyst was prepared according to the procedure disclosed in
Example 1 with the difference that 1.2 DMP was introduced into the
reactor in order to get Mg/1.2DMP=8 mol/mol.

[0066]The so prepared catalyst has then been used in the polymerization of
ethylene according to the general polymerization procedure (first run
with TEAL second run with TIBAL). The results are shown in Table 1.

EXAMPLE 7

[0067]Into a 2 l glass reactor provided with stirrer, were introduced 1 L
of TiCl4 and 70 g of the support prepared as described in the
example 1. The whole mixture was heated and kept under stirring for 30
minutes at 75° C. After that, stirring was discontinued and the
liquid siphoned off. At room temperature, 1 of fresh TiCl4 was
introduced and immediately, 7.2 mL of 1,2 DMP (Mg/1,2DMP=8 mol/mol) were
added stirring the slurry. Then, the mixture was heated at 100° C.
and kept under stirring for 60 minutes. After that, stirring was
discontinued and the slurry settled for 180 minutes. Then the liquid was
siphoned off.

[0068]Two washings with fresh hexane (1 liter) were carried out at
60° C. and then two additional hexane washings were performed at
room temperature. The spherical solid component was discharged and dried
under vacuum at about 50° C.

[0070]The so prepared catalyst has then been used in the polymerization of
ethylene according to the general polymerization procedure (first run
with TEAL second run with TIBAL). The results are shown in Table 1.

COMPARISON EXAMPLE 1

[0071]A catalyst component was prepared according to the same procedure
described in Example 1 with the only difference that the electron donor
compound of formula (I) was not used.

[0072]The said catalyst has then been used in the polymerization of
ethylene according to the general polymerization procedure (first run
with TEAL second run with TIBAL). The results are shown in Table 1.